KarmaGuiOpenGLHandler.h

// Major and heavy modifications of the original Dear ImGUI's take on OpenGL3 implementation
// https://github.com/ravimohan1991/imgui/blob/07334fa9c67e6c7c827cc76c2ac4de419a1658c1/backends/imgui_impl_opengl3.h
 
#pragma once
#include "KarmaGui.h"      // IMGUI_IMPL_API
#include "Karma/Renderer/Scene.h"
 
#define KGGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
 
//#include "glad/glad.h"
 
#ifdef _WIN64
typedef signed   long long int khronos_ssize_t;
#else
typedef signed   long  int     khronos_ssize_t;
#endif
 
typedef unsigned int GLuint;
typedef int GLint;
 
typedef khronos_ssize_t GLsizeiptr;
 
 
namespace Karma
{
    // Decal data
    struct MesaDecalData
    {
        GLuint DecalRef;
        KGTextureID DecalID;
        int width, height;
    };
 
    // OpenGL Data
    struct KarmaGui_ImplOpenGL3_Data
    {
        GLuint          GlVersion;               // Extracted at runtime using GL_MAJOR_VERSION, GL_MINOR_VERSION queries (e.g. 320 for GL 3.2)
        char            GlslVersionString[32];   // Specified by user or detected based on compile time GL settings.
        GLuint          FontTexture;
        // Images data
        std::vector<MesaDecalData>  openglMesaDecalDataList;
        GLuint          ShaderHandle;
        GLint           AttribLocationTex;       // Uniforms location
        GLint           AttribLocationProjMtx;
        GLuint          AttribLocationVtxPos;    // Vertex attributes location
        GLuint          AttribLocationVtxUV;
        GLuint          AttribLocationVtxColor;
        unsigned int    VboHandle, ElementsHandle;
        GLsizeiptr      VertexBufferSize;
        GLsizeiptr      IndexBufferSize;
        bool            HasClipOrigin;
        bool            UseBufferSubData;
        //KarmaGui_ImplOpenGL3_Data() { memset((void*)this, 0, sizeof(*this)); }
    };
 
    // OpenGL vertex attribute state (for ES 1.0 and ES 2.0 only)
#ifndef KGGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
    struct ImGui_ImplOpenGL3_VtxAttribState
    {
        GLint   Enabled, Size, Type, Normalized, Stride;
        GLvoid* Ptr;
 
        void GetState(GLint index)
        {
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_ENABLED, &Enabled);
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_SIZE, &Size);
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_TYPE, &Type);
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_NORMALIZED, &Normalized);
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_STRIDE, &Stride);
            glGetVertexAttribPointerv(index, GL_VERTEX_ATTRIB_ARRAY_POINTER, &Ptr);
        }
        void SetState(GLint index)
        {
            glVertexAttribPointer(index, Size, Type, (GLboolean)Normalized, Stride, Ptr);
            if (Enabled) glEnableVertexAttribArray(index); else glDisableVertexAttribArray(index);
        }
    };
#endif
 
    class KARMA_API KarmaGuiOpenGLHandler
    {
    public:
        // Backend API
        static bool KarmaGui_ImplOpenGL3_Init(const char* glsl_version = NULL);
        static void KarmaGui_ImplOpenGL3_Shutdown();
        static void KarmaGui_ImplOpenGL3_NewFrame();
        static void KarmaGui_ImplOpenGL3_RenderDrawData(KGDrawData* draw_data);
        /*
        inline static KarmaGui_ImplOpenGL3_Data* KarmaGui_ImplOpenGL3_GetBackendData()
        {
            return KarmaGui::GetCurrentContext() ? (KarmaGui_ImplOpenGL3_Data*)KarmaGui::GetIO().BackendRendererUserData : NULL;
        }*/
 
        static void KarmaGui_ImplOpenGL3_SetupRenderState(KGDrawData* draw_data, int fb_width, int fb_height, GLuint vertex_array_object);
        static void KarmaGui_ImpOpenGL3_SetupRenderStateFor3DRendering(Scene* sceneToDraw, KGDrawData* drawData);
        static bool CheckShader(GLuint handle, const char* desc);
        static bool CheckProgram(GLuint handle, const char* desc);
        static void KarmaGui_ImplOpenGL3_RenderWindow(KarmaGuiViewport* viewport, void*);
        static void KarmaGui_ImplOpenGL3_InitPlatformInterface();
        static void KarmaGui_ImplOpenGL3_ShutdownPlatformInterface();
        static void KarmaGui_ImplOpenGL3_CreateTexture(char const* fileName, const std::string& label = "");
 
        // (Optional) Called by Init/NewFrame/Shutdown
        static bool KarmaGui_ImplOpenGL3_CreateFontsTexture();
        static void KarmaGui_ImplOpenGL3_DestroyFontsTexture();
        static bool KarmaGui_ImplOpenGL3_CreateDeviceObjects();
        static void KarmaGui_ImplOpenGL3_DestroyDeviceObjects();
    };
}